This invention relates to a positioning joint for a folding ladder.
In a conventional positioning joint for a folding ladder, the folding or unfolding of the ladder to a desired angular position is performed by a rachet acting to permit or hinder engagement of a locking element in the respective notches by disclosing or closing the appropriate notch. A joint of this type raises concerns about the safety of such a joint because of potential malfunctions of the rachet.
Another prior art joint for a folding ladder utilizes a clawed control means, as set forth in U.S. Pat. No. 4,540,306, but which has a drawback in that it malfunctions easily unless the user exercises great care in operating the ladder to the desired angular position and a further disadvantage in that it is difficult to manufacture the joint because of the use of a tension spring.
A further positioning joint for a folding ladder is set forth in U.S. patent application Ser. No. 106,818 in which two joint members are relatively pivotable about a common axis, and are lockable in a series of predetermined angular positions by engaging a locking device provided within one member in notches formed at the peripheral edge of the other member, under the control of a guide-disc plate.
Although this type positioning joint insures safety in use while being easy to operate, it has a drawback in that its construction is somewhat complex and costly to manufacture, and has a further disadvantage in that it sometimes has problems in use while being difficult to repair.